Stereophonic reverberation system



22, 1964 K. SCHJONNEBERG 3,162,727

S TEREOPHONIC REVERBERATION SYSTEM Filed Aug. 25, 1961 FIGJ. l6 I8 l7 RIGHT PRE-AMP. A GHANNEL R AMPLIFIER 26 REVERBERATION REVERBERATION 2 DELAY smmu. (u-m DEVICE g AMPLIFIER as 27 "l 24 LEFT PRE-AMP.

CHANNEL L LEFT AMPLIFIERi FIG.2.

INVENTORI KNUT SCHJONNEBERG HIS ATTORNEL United States Patent 3,162,727 STEREGPHONIC REVERBERATION SYSTEM Knut Schjonneberg, Syracuse, N.Y., assignor to General Electric Company, a corporation of New York Filed Aug. 25, 1961, $91. No. 134,017 7 Claims. (Cl. 179-1) This invention relates to stereophonic audio systems, and particularly to stereophonic audio systems provided with a reverberation effect. Such audio systems are useful in connection with stereophonic phonographs, stereophonic tape players, stereophonic radios, and the like.

Stereophonic reverberation audio systems, of the type having left and right signal channels, have beenprovided with a signal delay device to which the left and right signals of two stereo channels are fed, the delayed sum signal being recombined with the left and right stereophonic signals in the stereophonic signal channels, so that the audible signals emitted by each of the left and right stereophonic loudspeakers contains a delayed or reverberation sum component of the left and right signals which creates a pleasing illusion of being in a large auditorium or concert hall. However, when the reverberated sum of the two stereophonic signals is thus added to the left and right stereophonic channels, the listener experiences a loss of spread of the stereophonic sounds from the loudspeakers, i.e., the source of the total sound image seems to become narrower. This results in a partial loss of the stereophonic effect.

An object of the present invention is to provide a stereophonic reverberation system which obviates the abovementioned drawbacks.

A further object of my invention is to provide an improved stereophonic reverberation system.

Another object of this invention is to provide reverberation in a stereophonic system without degrading the stereophonic effect.

A further object is to provide a more realistic reverberation effect in a stereophonic sound system.

Still other objects will be apparent from the following description and claims, and from the drawing in which:

FIG. 1 is an electrical diagram, mainly in block form, of a preferred embodiment of the invention; and

FIG. 2 is a top view of a room, showing a preferred arrangernent of loudspeakers with respect to a listener, in accordance with the invention.

The invention comprises, basically, a stereophonic audio system of two or more channels along with their associated loudspeakers, the system being provided with means for adding together the stereophonic signals of the channels to obtain a sum signal, reverberation means for reverberating or delaying the sum signal, and a reverberation loudspeaker system of one or more loudspeakers to which the reverberated sum signal is applied. Thus, the sound from the stereophonic speakers is not contaminated with any delayed sum signal, and hence the full stereo effect is achived, while at the same time a reverberation effect is achieved by the delayed sum signal sound from the reverberation loudspeaker system. The invention furthercomprises a stereophonic reverberation arrangement having the stereophonic loudspeakers arranged in normal spaced relationship in front of a listener, and wherein the reverberation loudspeaker system comprises two loudspeakers respectively positioned to the left and to the right of the listener. Each of these reverberation loudspeakers emits the delayed sum signal. The effect of this arrangement is to enhance the normal sound deflections from the room walls, by providing a delayed sound component of adequate loudness which creates the illusion of the room walls being farther away from the listener. Thus, the room seems acoustically larger than its actual size.

3,l62,727 Patented Dec. 22, 1964 Now referring to FIG. 1 of the drawing, a preferred circuit of the invention is shown in combination with a stereophonic phonograph pickup cartridge 11 equipped with a stylus 12 for playing from a stereophonic phonograph record 13. The right stereophonic signal from the pickup cartridge 11 is fed through a preamplifier 16 to a right channel conductor 17, and hence through a right channel amplifier 18 and is then applied to a right stereophonic loudspeaker 19. The left stereophonic signal from the cartridge 11 is fed through a preamplifier 21 to a left channel conductor 22, from which the signal is fed through an amplifier 23 and applied to a left loudspeaker 24. The cartridge 11 can, of course, be replaced by another source of sterephonic signals.

A pair of resistors 26 and 27 is connected in series between the left and right channel conductors 17 and 22, so as to provide at the junction 28 thereof the sum of the left and right stereophonic signals. This sum signal is fed through a reverberation delay device 29, which may comprise any known acoustical, electrical, or mechanical type of signal delay arrangement. Some examples of reverberation delay devices are described in US. Patent 2,318,417, issued to W. D. Phelps on May 4, 1943, and assigned to the same assignee as the present invention. The output of the delay device 29 is connected to a reverberation signal amplifier 31, which amplifies the reverberated sum signal and applies it to a reverberation loudspeaker system 32. The loudspeaker system 32 may comprise one or more loudspeakers suitably located with respect to the left and right loudspeakers 19 and 24, and with respect to the listners, to provide a pleasing reverberation effect. A convenient location for the reverberation loudspeaker system 32 is intermediate or midway between the stereophonic loudspeakers 19 and 24, as shown in FIG. 1.

The listener will hear the stereophonic left and right signals, in normal and optimum manner, from the left and right loudspeakers 19 and 24, the sounds from these stereophonic loudspeakers being uncontaminated by any part of the delayed sum signal. On the other hand, the reverberated signal or sound supplied by the reverberation loudspeakers 32, suitably creates a reverberation effect of concert hall realism.

A preferred arrangement of the loudspeakers of the invention, as shown in FIG. 2, comprises placement of the left and right loudspeakers 19 and 24 in spaced relationship in front of the listener 25 in the normal manner, and the reverberation loudspeaker system 32 comprises a pair of loudspeakers 32a and 32b to which the reverberated sum signal is fed. The loudspeakers 32a and 3212 are respectively positioned to the left and to the right of the listener 25, so that the reverberated signal comes to the listener 25 from the directions of the side walls 33, 34 of the room in which the equipment is located. By suitably adjusting the loudness of the reverberated signal which is emitted from the loudspeakers 32a and 32b, this being readily accomplished by means of a reverberation volume control 36 in the reverberation circuit, the arrangement gives the illustion to the listener 25 that the reverberated signal from the loudspeakers 32a and 32b is the reflection from the walls 33 and 34 of the stereophonic signals from the loudspeakers 19 and 24, i.e., the reverberated signal is loud enough so that it overrides the signals from the loudspeakers 19 and 24 which reflect to the listener 25 from the walls 33 and 34. By giving the reverberation device 29 a time delay greater than the actual time delay incurred by acoustic waves traveling to the listener 25 from the loudspeakers 19 and 24 via reflections from the walls 33 and 34, the listener Z5 is given the illusion of the walls 33 and 34 being acoustically farther away than they actually are. This provides 0 the illusion of the listening room being larger than it is, thus giving an efifect of concert hall realism. It is found that this desirable effect is adequately provided by the arrangement shown and described in which each of the reverberation loudspeakers 32a and 32b emits the reverberated sum of the stereophonic signals.

While a preferred embodiment of the invention has been shown and described, other embodiments and modifications thereof will become apparent to those skilled in the art, and are within the scope of the invention as defined in the following claims. For example, the invention may be applied to stereophonic systems having more than two channels, by reverberating the sum of the signals of some or all of the channels.

What I claim is:

1. A reverberation arrangement for a stereophonic system having at least two stereophonic signal channels connected to at least two stereophonic loudspeakers for producing stereophonic sound waves at a listening area, said arrangement comprising means providing a sum signal of the signals of at least two of said channels, signal reverberation delay means connected to receive said sum signal and adapted to delay said sum signal, and a loudspeaker system other than said stereophonic loudspeakers connected to receive the delayed sum signal and adapted to produce the said delayed sum signal in the form of reverberated sound waves at said listening area simultaneously with said stereophonic sound waves.

2. An arrangement as claimed in claim 1, in which said loudspeaker system is located between two of said stereophonic loudspeakers.

3. An arrangement as claimed in claim 1, in which said loudspeaker system comprises at least two loudspeakers adapted to be respectively positioned to the left and to the right of said listening area.

4. A reverberation arrangement for a stereophonic system having at least two stercophonic signal channels connectedto at least two stereophonic loudspeakers for producing stereophonic sound waves and positioned in sideways spaced relationship in front of a listening area in a room, said arrangement comprising means providing a sum signal of the signals of at least two of said channels, signal reverberation delay means connected to receive said sum signal and adapted to delay said sum signal, at least two reverberation loudspeakers other than said stereophonic loudspeakers respectively positioned to the left and to the right of said listening area, and means to apply said delayed sum signal to said reverberation loudspeakers whereby said reverberation loudspeakers produce reverberated sound waves simultaneously with said stereophonic sound waves.

5. An arrangement as claimed in claim 4, including means to adjust the volume of sound from said reverberation loudspeakers to a value so that the loudness of said reverberated sound waves at said listening area is greater than that of the stereophonic sound waves that are reflected from the sidewalls of said room.

6. An arrangement as claimed in claim 4, in which said signal delay means delays said sum signal for a time interval greater than the time interval required for said stereophonic sound waves to reach said listening area via reflection from the sidewalls of said room.

7. An arrangement as claimed in claim 6, including means to adjust the volume of sound from said reverberation loudspeakers to a value so that the loudness of said reverberated sound waves at said listening area is greater than that of the stereophonic sound Waves that are refiected from the sidewalls of said room.

References Cited by the Examiner UNITED STATES PATENTS 1/58 Bogert 179-100.1 6/60 Volkmann l79-1 ROBERT H. ROSE, Primary Examiner.

THOMAS B. HABECKER, Ext/miner. 

1. A REVERBERATION ARRANGEMENT FOR A STEREOPHONIC SYSTEM HAVING AT LEAST TWO STEROPHONIC SIGNAL CHANNELS CONNECTED TO AT LEAST TWO STEROPHONIC LOUDSPEAKERS FOR PRODUCING STEROPHONIC SOUND WAVES AT A LISTENING AREA, SAID ARRANGEMENT COMPRISING MEANS PROVIDING A SUM SIGNAL OF THE SIGNALS OF AT LEAST TWO OF SAID CHANNELS, SIGNAL REVERBERATION DELAY MEANS CONNECTED TO RECEIVE SAID SUM SIGNAL AND ADAPTED TO DELAY SAID SUM SIGNAL, AND A LOUDSPEAKER SYSTEM OTHER THAN SAID STEROPHONIC LOUDSPEAKERS CONNECTED TO RECEIVE THE DELAYED SUM SIGNAL AND ADAPTED TO PRODUCE THE SAID DELAYED SUM SIGNAL IN THE FORM OF REVERBERATED SOUND WAVES AT SAID LISTENING AREA SIMULTANEOUSLY WITH SAID STEROPHONIC SOUND WAVES. 